Long, bright glass is hard to come by, but Canon didn’t wait long before bringing its 400mm f2.8 over to the RF mount. The Canon RF 400mm f2.8 L IS USM brings the same optics as the EF 400mm f2.8 IS III USM to cameras like the R3 and R5 without the use of a mount adapter. As part of the L series, it uses both a high-end, weather sealed build and pro level optics. Lenses of this stature are pricey, however, and the new Canon RF 400mm f2.8 is no exception. The glass retails for just under $12K.

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But, paired with features like eye AF and exceedingly fast shutter speeds, the Canon RF 400mm f2.8 gives the newest mirrorless cameras the reach for sports and wildlife photography. I took the Canon RF 400mm f2.8 out birding to see how this new optic holds up. The lens used in this review was provided by LensRentals.

The Canon RF 400mm f2.8 is a heavy piece of glass, but it captures some wonderful images. With little aberration and lots of background blur, this lens produces some wonderful shots. The autofocus is also excellent. But, that $12K is a high price to pay.

I tested the Canon RF 400mm f2.8 with the following gear:

The 400mm lens was a rental from LensRentals.

To bring super telephotos to the RF mount quickly, Canon reused the optical design from the EF 400mm f2.8 IS III USM. It shares enough qualities of the EF mount lens that owners of the older optic who are switching to mirrorless will want to see how well the EF lens focuses on the RF camera before considering RF mount. While this lens doesn’t offer any dramatic new technologies, Canon is adding more full-frame mirrorless super telephotos at a faster rate than Nikon or Sony.

LensRentals lists the following specifications:

I tested the Canon RF 400mm f2.8 alongside the RF 600mm f4 lens. The two lenses are ergonomically similar, with the 400mm being a bit shorter and lighter, trading the shorter focal length for a brighter aperture. Because the two lenses have a similar control scheme, alternating between them is straightforward. But, with the weight of the two lenses, carrying both at once isn’t easy.

The Canon RF 400mm f2.8 feels like a cannon (lowercase C, three Ns). It’s a 14.4-inch lens that weighs almost 6.5 pounds. Handholding this lens was a workout; I was exhausted at the end of my hike. It’s possible to handhold thanks to the built-in stabilization, but when it’s practical, a monopod will make shooting more enjoyable.

At the top of the lens just after the silver detailing by the mount, two silver buttons press in to pull out a drop-in filter. This allows the lens to take 52mm filters, since fitting the large front of the lens with a filter would be impractical. 

Just underneath the drop-in filter is the first bank of control switches, resting within reach of the left hand. The top switch is the AF to MF switch. This lens also has a PF mode, which uses the smaller ring at the front of the lens for power focusing: a feature geared towards video because of the faster, smoother transitions. Underneath that is the focus limiter switch.

Continuing out from the mount, the next part of the lens is the tripod collar. A twist knob loosens the collar, allowing it to adjust to shoot vertically. The base of the collar has two tripod mounting screws, along with a grippy texture for using the collar to support the weight of the lens when shooting handheld.

The second bank of control switches is twice the size of the first. At the top are two switches for the stabilization system. The first has three different stabilization modes; the second turns stabilization on and off. A set button separates the top two switches from the bottom two. This button sets the different focus positions when using the focus preset feature on the front ring. The next switch turns the focus preset off, on, or on with sound. The final switch adjusts the speed of the manual focus ring.

The Canon RF 400mm f2.8 has two rings. The large, grippy black ring adjusts manual focus. The thinner textured white ring is the power focus and focus preset switch. Depending on the settings on the switches, this ring can be used to quickly go back and forth between two pre-set focal distances, or as a power focus ring. The 400mm lens looks like it has a third ring in the pictures — but that final ring of black is just added grip. Four evenly-spaced buttons around this ring can be used to temporarily pause autofocusing.

The front of the lens is mostly glass, without any wide plastic edging. It shows off a nine-blade aperture inside.

Because of the size and price of this lens, it doesn’t ship with the usual accessories. Instead of a plastic lens cap, it includes a soft, padded slipcover. The lens also ships with an excellent bag that accommodates the size of the lens and uses a single sling strap for wearing the lens on your back. This is a nice feature since few camera bags are made to accommodate such a large lens.

The Canon RF 400mm f2.8 is heavy enough without being a metal lens. But, the barrel doesn’t feel like cheap plastic. It feels solid in the hands — though those hands are a bit too busy managing the weight of the lens to appreciate the feel. 

As part of the L series, this lens is weather-sealed. I gave the lens a good dousing with a cup full of water, and everything continued to function normally. The dust and weather-sealing feel solid.

The part of the lens that I see wearing out first is the white paint job. I tested a rental lens, and there was some minor wear on the paint around the tripod mount and a few other scuffs on the body. This is all cosmetic, but noteworthy. 

With fewer pieces to move a shorter distance, the Canon RF 400mm f2.8 had a better hit rate than the 600mm lens, which was already excellent. When birding with this lens, only around two to three percent of the images were soft. The autofocus motor works on subjects as close as 8.2 feet from the lens, which is excellent for such a long focal length.

There were a few instances where birds in flight were too soft, most often when working with smaller songbirds that don’t take up much of the frame. On a larger subject, like my dog running full speed towards the camera, the autofocus was near perfect. The one or two shots that missed focus on his face got his ears and shoulders. I also had a few stretches of images where the focus didn’t transition quite fast enough — the focus limiter switch should help with this. But, 98 percent of the time, this lens did spectacularly. 

The R3 is Canon’s best autofocusing body at the moment and it’s a pretty spectacular pairing. The animal eye AF on the R3 is the best I’ve tested so far. With it, the 400mm was able to pick out birds from a mess of branches that would have been difficult for most systems to find.

For the best results, photographers should familiarize themselves with this lens enough to locate the AF limiter switch blindly and to learn how to use the focus preset feature. With that, the RF 400mm will deliver plenty more sharp shots than soft ones.

The L series is made for Pros, and the controls on the Canon RF 400mm f2.8 reflect that. Photographers will need to spend some time with this lens for seamless use. Learning to find the AF limiter switch without pulling the eye from the viewfinder, for example, will take some time. The switches all have the same feel to them, so this is done only by position.

There are a few options on this lens that are typically found only on longer luxury glass. Despite having used several L series lenses, I had to dig up the instructions for using the Focus preset feature and learn what that PF on the focus mode switch meant. But, once familiar, those switches will help users get the most out of this lens.

Still, the trickiest part of using this lens is its sheer size. Pointing and shooting is simple enough. But, when it’s a matter of pointing and waiting for the subject to do something interesting, the weight of the lens makes it harder to handhold for long stretches. It’s a large enough lens that it’s easier to twist the body onto the lens rather than twist the lens onto the body.

The combination of the 400mm focal length and the bright f2.8 aperture is bokehlicious. When using that 8.2-foot minimum focus capability, the background becomes a solid, creamy color. The lens is sharp, with only some minor fall off at the corners and there’s little in the way of chromatic aberration, vignetting, or pincushion distortion.

Aim this lens at something with similar colors, and the background melts away as if shot against a studio background. The focal length, aperture, and close focusing capabilities work well together for soft, creamy backgrounds. The subject really stands out while the rest of the scene has more depth than lenses with narrower apertures.

Points of light are mostly round with soft edges. I didn’t spot onion ringing or soap bubble effects. Because of the longer focal length, the bokeh has a lower tendency to cat-eye towards the edges than shorter lenses. The bokeh balls remain mostly round even towards the edges.

Could Canon have made this lens sharper by starting from scratch instead of borrowing the optical design of the EF lens? Perhaps. But I’m not sure you’d notice it outside a laboratory setting. The lens is sharp and creates excellent detail. I was surprised at how well I could see the fine details on individual features and how much I was able to crop in in post. There is a slight softness to the corners at f2.8, but it will rarely be noticed out in the field.

There’s little barrel or pincushion distortion here to pick up on. Similarly, I didn’t find any overwhelming chromatic aberration or vignetting. This lens lives up to the L series standard.

Directed towards the sun, it produces a soft, white flare with reduced contrast. At the right angle, there’s occasionally a spot of colored ghosting circles, but not often.

Without many aberrations or colored flare to fight, the colors from this lens feel like an ideal balance between realistic and rich. The JPEGs look excellent. On the RAW files I chose to edit, I didn’t have to mess with odd color casts. I edited for style, without feeling the need to edit for accuracy.

From day one, The Phoblographer has been huge on transparency with our audience. Nothing from this review is sponsored. Further, lots of folks will post reviews and show lots of editing in the photos. The problem then becomes that anyone and everyone can do the same thing. They’re not showing what the lens can do. So we have a section in our Extra Image Samples area to show edited and unedited photos. From this, you can make a decision for yourself.

The Canon RF 400mm f2.8 L IS USM is an excellent piece of glass. The bokeh is dreamy while subjects remain sharp. The autofocus has a great hit rate even with action. And the durability and control scheme is made for pros.

However, this lens comes at a high cost. While the 400mm mixed and the f2.8 create a depth that’s difficult to find, it also costs a pretty $12K. That price will put it out of reach for hobbyists. Canon also borrowed the optics of the EF lenses to make this lens, and I wonder if they could have made it smaller if they made more changes. But, for the pros who can afford the cost and carry the weight, the reward is some dreamy images full of depth and detail.

I’m giving the Canon RF 400mm f2.8 L IS USM five out of five stars. Want one? You can pick one up at Adorama or rent one from LensRentals.

Hillary K. Grigonis is a photographer and tech writer based in Michigan. She shoots weddings and portraits at Hillary K Photography. A mother of three, she enjoys hiking, camping, crafting, and reading.